I've not read it in detail but I think it turns on whether it's compatible with article 8 right (private and family life) and article 14 (non-discrim) for health care to be unevenly delivered in this way. they have treated it as if she was going to access any other procedure that wasn't available to her locally on the NHS.
It's interesting that Lady Hale, the only woman, took a different view. She thinks anyone who is resident anywhere in the UK should be able to travel to access a free abortion, and maybe even anyone from anywhere in the world.
From Lord Wilson's judgement:
' Lady Hale also suggests that the duty of the NHS in England to provide abortion services extends even to foreign citizens present in England; but its entitlement to charge such citizens, which Lady Hale recognises, might not negate the effect of the suggested extension on the functioning of the service. Irrespective, however, of its precise extent, the duty proposed to be cast upon the respondent by Lord Kerr and Lady Hale would, in my view, precipitate both a substantial level of health tourism into England from within the UK and from abroad and a near collapse of the edifice of devolved health services.'